Many manufacturing processes produce waste streams which, if expelled from plants without further treatment, pollute the environment. Failure to treat these waste streams also results in the loss of valuable materials which can be recovered and reused in the manufacturing process. Moreover, the Federal government regulates the concentrations of certain materials in effluent streams. It has been especially difficult to treat very dilute waste streams economically, such as those which are produced by plating processes and related rinsing operations, in particular, electroless plating processes. Attempts have been made to use sulphide precipitation and starch xanthate processes for this purpose, but they have proven expensive, difficult to control. Further, they produce precipitate end products which are hard to flocculate and filter.
Many plating processes produce, inter alia, waste streams having dilute concentrations of metal ions which are complexed with organic molecules. Metal ions exist in waste streams in a complexed form with a chelating agent. Regulations set very strict standards for metal ion concentrations in the effluent from these processes. Moreover, the metal ions and chelating agents in the waste streams are valuable and have the potential to be recycled through the process. There have been many attempts to recover the chemicals from these waste solutions.
For example, it has been suggested that an ion exchange resin which acts as a very powerful complexing agent selectively removes copper from the copper complexes in the effluent. One such resin has an iminodiacetic functional group (R. M. Spearot et al., "Recovery Process for Complexed Copper Bearing Rinse Waters", Environmental Progress, Vol. 3, No. 2, p. 124, 1984). However, this resin was unable to remove copper from effluent in the presence of ethylenediaminetetraacetic acid (EDTA), a complexing agent which is often used in electroless plating processes.
It is generally believed that using an anionic exchange resin to remove transition metal ions complexed with a compound in the plating bath rinse, such as EDTA, would not operate to remove these complexes because the anions of the salts in the bath rinse would be more strongly attracted to the resin than the ions, complexes or complexing agents to be removed.
It has been suggested to treat an anionic exchange resin with EDTA, for example, and utilize the treated resin to chromatographically separate metals from a solution.
Courdevalis, et al. have suggested trying to remove copper from its complexes by using a resin prepared by reacting polyethyleneimine with chloracetic acid and cross-linking the polymer (Plating and Surface Finishing, "A New Treatment for Wastewater Containing Metal Complexes", March 1983, p. 70 and U.S. Pat. No. 4,303,704). This method was unsuccessful in removing copper from an EDTA complex, although it could be used to remove copper from a solution containing tartrate, or an organic acid ester or N,N,N',N' tetrakis-(2 hydroxypropyl) ethylene diamine, an alkanolamine chelator.
U.S. Pat. No. 4,076,618 describes the use of strong cationic resin with a sulfonic or carboxylic acid functional group to extract cupric ion and alkanolamine chelator complexes.
It is, therefore, an object of this invention, to provide a process for removing metals from waste solutions such that the waste solutions meet levels dictated by regulation.
It is a further object of this invention to provide a process to remove chelated copper ions which are complexed with a wide variety of complexing agents from waste solutions.
It is still a further object of this invention to provide a process to remove copper EDTA complexes from waste solutions.